Conference Agenda

In this work, a pyrohydrolysis method was proposed as a sample preparation procedure and further determination of halogens in commercial drugs used for treatment of hypertension and depression. Inductively coupled plasma mass spectrometry (ICP-MS) was used for for Br and I determination, ion chromatography (IC) for F and Cl determination, and potentiometry with ion-selective electrode (ISE) for F determination. The influence of the following parameters involved in the pyrohydrolysis reaction were evaluated: temperature, reaction time, sample mass, absorbing solution, carrier gas flow rate, water flow rate, and need for the use of auxiliary reagents. It was observed that, under the experimental conditions employed, better RSDs (< 10%) were obtained by using of 1000 °C of temperature for 10 min of reaction and with a carrier gas flow rate of 0.2 L min^-1. Relatively high sample mass (500 mg) was used and for some cases sample was mixed with 500 mg of SiO₂, and insertion speed of boat into the reactor of 0.03 cm s^-1. The results were compared with those obtained by the reference method using microwave-initiated combustion (MIC) and the obtained results did not differ significantly (t-test, with a confidence level of 95%). Accuracy was evaluated using certified reference materials and by using standard addition recovery assays in three levels (50, 100, and 150%). The results obtained were in agreement with the reference values and with the addition of analyte in more than 90%. The quantification limits obtained were better than 15 μg g⁻¹ for F and Cl by IC, better than 0.036 μg g⁻¹ for Br and I, respectively by ICP-MS, and 3.0 µg g^-1 for F by ISE. The proposed pyrohydrolysis method proved to be suitable for the determination of halogens in drugs with minimal use of reagents and waste generation and providing digests completely compatible with multitechnique determination (ICP-MS, IC and ISE).

Advances in instrument technologies in the recent decade have led to significant improvements in the time resolution for Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS). On the one hand, rapid response cells were developed allowing for the fast washout and therefore detection of the material generated during laser ablation. On the other hand, the time resolution of the mass spectrometers improved greatly, owing partly to the establishment of Time-of-Flight detectors for coupling with LA, but also to the reduction in settling time for newer generation quadrupole-based systems. This enabled the investigation of the signal response of individual laser shots, the so-called Single Pulse Response (SPR), which offers new possibilities for spatially resolved analyses.

However, investigations of the SPR of gelatine carried out by van Helden et al.^{1, 2} revealed that some elements (e.g., C, Zn, and Hg) exhibit a bimodal SPR profile, which they attributed to a separation of the ablated material into a particulate and a gaseous phase. This separation was already reported earlier^{3, 4}, but especially when using the SPR concept it can have negative effects on image quality² and may limit the applicability of internal standards.⁴ The latter is particularly significant, seeing that carbon is often used as an internal standard in bioimaging, but also seems a intuitive choice for, e.g., synthetic polymers.

In this contribution, we investigate the two-phase sample transport resulting from the ablation of different synthetic polymers, namely polyimide (PI), poly(methyl methacrylate) (PMMA), polyvinylpyrrolidone (PVP), polysulfone (PSU), and polyvinyl chloride (PVC). The main focus is the SPR profile of carbon, but the signals of sulfur (for PSU) and chloride (for PVC) are discussed too. Parameters influencing the SPR profile (laser energy, spot size, ablation cell parameters) are examined and their impact on the sensitivity for trace analytes is analyzed.

Based on these findings, we discuss the consequences of the two-phase sample transport for different matrices and how this places preconditions on the samples and experimental setup, in order to ensure proper quantification for analytes. In the future, we are aiming to utilize the found relationships between laser parameters, polymer type, etc., to analyze real-life samples containing different polymers, enabling the spatially resolved, matrix-matched quantification of trace elements in the corresponding sample regions.

(1) Van Helden, T.; Mervič, K.; Nemet, I.; van Elteren, J. T.; Vanhaecke, F.; Rončević, S.; Šala, M.; Van Acker, T. Evaluation of two-phase sample transport upon ablation of gelatin as a proxy for soft biological matrices using nanosecond laser ablation – inductively coupled plasma – mass spectrometry. Analytica Chimica Acta 2024, 1287, 342089. DOI: https://doi.org/10.1016/j.aca.2023.342089.

(2) van Elteren, J. T.; Van Helden, T.; Metarapi, D.; Van Acker, T.; Mervič, K.; Šala, M.; Vanhaecke, F. Predicting image quality degradation as a result of two-phase sample transport in LA-ICP-TOFMS mapping of carbon-based materials. Journal of Analytical Atomic Spectrometry 2025, 40 (2), 520-528. DOI: https://doi.org/10.1039/D4JA00288A.

(3) Todolı́, J. L.; Mermet, J. M. Study of polymer ablation products obtained by ultraviolet laser ablation — inductively coupled plasma atomic emission spectrometry. Spectrochimica Acta Part B: Atomic Spectroscopy 1998, 53 (12), 1645-1656. DOI: https://doi.org/10.1016/S0584-8547(98)00219-5.

(4) Frick, D. A.; Günther, D. Fundamental studies on the ablation behaviour of carbon in LA-ICP-MS with respect to the suitability as internal standard. Journal of Analytical Atomic Spectrometry 2012, 27 (8), 1294. DOI: https://doi.org/10.1039/c2ja30072a.